Temperature-compensating spring



April l0, 1928.

J. PATRICK TEMPERATURE COMPENSATING SPRING Filed oct. 1o, 1.92'1

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www ML2 M practice to subject the movingg-partsto. thev .themxin the :opposite direction, .in f other Y Patented Apr. A10, 1928.

. ".TosHnA rammen, on Dnrnorrgamcnfieaiv;

"TEMPZERATUBEPCGMIENSATINGFSPRINGS i v Application: `filed;rctobcr'; 1l), `1921. Serial-.'NJGSWTI.

l .In-the construction of varioustypes of' indicating, andymeasu-ring instruments 1n which an indicating element isn moved.` im r one direction by meansres'ponsive-tovariatri-onse in physical. conditions, 1t is com-mon actiomoff-spri-ng'; means-tending to movel words, to stress Afth'e.- Iindicating:elemente toward the zero` s positlon A byfA resilient i means.

Seme` instrumentswof" this-,type :are @affected byvarlations in ftenaperature'-.of.` the environ-r :ingz .medium which change-z the capability orsensitiveness of the ,physical condition f responsive devices. Wellylmown. .examples .of devices of this type are the speedometers,

` tachometers...andsthe like.which utilize. Jthe flux produced'by relative rotation'ofa magnet and?armagneticrmassvto cause deflection A l of a non-magnetic element pivotally `supported in the magnetic field. Since'the conductivity of the drag element decreases with increase of temperature, the deflectioncorresponding to a given speed of relative rota-4 tion also decreases, and where instruments ,of this type are subjectedto a `considerable range of environing temperature', the error vin indication becomes so great as'to Irequire i that some alloys suer 'a marked decrease in 4o Y compensation in some manner.

In accordance wlth the present Invention I propose to reduce the error due to temperature changes in connection withl instruments liable to such error by vselecting for c the resilient means operating to stress or bias the moving element toward zero position, a ,substance capable of inherently compensating, to a considerable extent, for the temperature error. I have found, `for example,

elasticity with increasing temperatures, a decrease which is sucient'to materially aiect the resilience of a spring constructed from such alloys, even within moderate 'vnetic speedometers, of which- Fig. 1 isa fragmentary sectional eleva-.c

tion, and Y Fig. 2 is a plan view on line 2-2 of Fig. 1. Y

K Referring to the .draw-ings: .5 indicatesfthe frame` oiga@ magnetic speedometer. especially. designed.: for.,4 motor vehicles', although .it'ei will be understood that theinvention-is-tinf'l nouv-uy'limiteduto use in instrumentsof this v forfarliollowfshaft?, driven bylflexibleshaft ing-18-and c-arryingat theupper'end a mag;- nctic unass .QQarranged to,` rotate v within-1. thea field ot a permanent' magnet'l 10.- .15e-so called speed cup 11, upon the periphery of'- which`V suitable. indicaftiiflgy characters may be arranged, is` interposed. betweenthetpoles ot'. the; In agnetf` andrV the. rotor.l 9. iin such.y rc'la-V u tion as. to beaii'ected inductivelyr when the Vmassis rotated. The cupis;supported,upon

a spindle 12 supported in l, bearings. 13,114.1` y

the 'frame' 5 as by screw 16'.. .'.Th'efmateriali of the speed cup may be, and'pre'ferably is, of a special alloy such, for example,A as magnalium, the use of which for this pur. pose is disclosed in my copending applica.- tion Serial VNo. 502,524, filed Septembery22, 1921. Thespeed cup is stressed toward zero position, in opposition to the inductive drag due toy the relative 'rotation betweenA the magnet and rotor, by a springl? shown as of a flat spiral form. This biasing sprin'gisv attached at its vinner and outer ends respecf tively to the spindle of the ldrag element or speedv cup and to a fixed part of the fra-me.

The means vof attachment may of course be varied greatly, Vbut 'as shown itA comprises, for'the inner end of the spiral, a pin18r securing the spring to a disk 19 formed on .the spindle 12, and, for the outer end, a

pin or wedge 20 adapted to clamp the end of the spring in an aperture formed in bracket 21 suitably secured, as by screw 22,

to the frame member 15. The spring 17 will be made,`in accordance with my invention, of a material having, to a marked extent, the property ofreduction of elasticity with increase inV temperature. By utilizing for this purpose the alloys whichV I Vhave found to possess the desired property, it is Apossible to reducefthe limits of error in instruments of the class referred to considerico ably below those obtainable even with the speedcup alloy of my copending application. The accuracy lof an instrument thus n constructed is quite` sutlicient for `practical purposes without the use of any accessory` thermostatic or like compensating devices.

' Among the alloys suitable for the purpose` herein set forth, mention may be made para Y ticularly of'brass andmagnaliuni, the latter Y comprising,.for this use, in the neighborhood of three per cent vof magnesium .and ninety-IL ieven'pcr cent of aluminum. Magnaliurn appears, from my experiments, to have a greater change in elasticity for the same range of temperature than any of the othersubstances In view of the lgeneral i:applicability o the invention, it Will be understood that va'- riations trom the speciiic disclosure herein` maybe made without departing from the spirit ot the invention or the scope of the appended claims.

I claim:

V1 Inl an indicating instrument the indi" cations of which are subject to error due to environing' temperature, the readingsbeing Y progressively lower as the temperature in;V

creases. a'biasing spring the elasticity of f which becomesless as temperature increases to such an extent as to 'alford compensation for the said error.

magnaliuniV by 2. An indicating instrument comprising a magnet and a magneticmass-,mountedor relative-rotation, a body arranged to be de-A ected by the inductive eilect of suchrotation, and a spring operative upon Said body, said spring of a material capable of affording compensation for error due to decrease in dctlectionof said body with increasing tern perature. Y Y V i Y 3. Structure as in' claim' 2, the yspring beingo'f material theelasticity of Whichde creases materially with incrcasingternperature Within climatic ranges.' l

4. Structureas inxclaimQ, the spring" ,being otmagnalium.

y5. A speedometer comprising` a magnet and-a magnetic mass arranged for-relative rotation, a speedv cup having portions inten' posed between the magnet and massk and adapted to be deflected from a zero position uponthe occurrence of relative rotation be- A tween said magnet and mass, and a Spring' arranged, to stressA said cup toward zero position,- said spring being vcomposed otriiz nf nalium. A c u v 'In testimonyv 'whereof IY attiX4 my signatureg JOSHUA 'ia/tiraron; 

